fix(agent): bound per-session file state

tests/agent/test_loop_session_policy.py

@@ -131,6 +131,7 @@ async def test_session_discard_control_cancels_active_turn(tmp_path, monkeypatch
         terminate_exec_sessions,
     )
     key = "websocket:transient-cancelled"
+    previous_file_state = loop._file_state_store.for_session(key)
     loop.sessions.get_or_create_transient(
         key,
         disabled_tools={"create_goal", "update_goal", "spawn", "cron"},
@@ -157,6 +158,7 @@ async def test_session_discard_control_cancels_active_turn(tmp_path, monkeypatch
         await asyncio.wait_for(active_task, timeout=2)
     await asyncio.wait_for(wait_for_discard(key), timeout=2)
     assert loop.sessions.get_cached(key) is None
+    assert loop._file_state_store.for_session(key) is not previous_file_state
     terminate_exec_sessions.assert_awaited_once_with(key)
 
     loop.stop()

tests/agent/test_unified_session.py

@@ -20,6 +20,7 @@ from unittest.mock import AsyncMock, MagicMock, patch
 import pytest
 
 from nanobot.agent.loop import AgentLoop
+from nanobot.agent.tools.file_state import FileStateStore
 from nanobot.bus.events import InboundMessage
 from nanobot.bus.queue import MessageBus
 from nanobot.command.builtin import cmd_new, register_builtin_commands
@@ -250,10 +251,16 @@ class TestCmdNewUnifiedSession:
         # asyncio.create_task().  Mirror that exactly so the coroutine is consumed
         # and no RuntimeWarning is emitted.
         admitted_runtime = MagicMock(name="admitted_runtime")
+        file_state_store = FileStateStore()
+        previous_file_state = file_state_store.for_session("unified:default")
+        tracked_file = tmp_path / "tracked.txt"
+        tracked_file.write_text("tracked", encoding="utf-8")
+        previous_file_state.record_read(tracked_file)
         loop = SimpleNamespace(
             sessions=sessions,
             consolidator=SimpleNamespace(archive=AsyncMock(return_value=True)),
             _cancel_active_tasks=AsyncMock(return_value=0),
+            discard_session_file_state=file_state_store.discard,
             llm_runtime=MagicMock(return_value=MagicMock()),
             schedule_background=lambda coro: asyncio.ensure_future(coro),
         )
@@ -278,6 +285,9 @@ class TestCmdNewUnifiedSession:
         sessions.invalidate("unified:default")
         reloaded = sessions.get_or_create("unified:default")
         assert reloaded.messages == []
+        reset_file_state = file_state_store.for_session("unified:default")
+        assert reset_file_state is not previous_file_state
+        assert reset_file_state.is_unchanged(tracked_file) is False
         loop.consolidator.archive.assert_called_once_with(
             expected_snapshot,
             runtime=admitted_runtime,
@@ -302,6 +312,7 @@ class TestCmdNewUnifiedSession:
             sessions=sessions,
             consolidator=SimpleNamespace(archive=AsyncMock(return_value=True)),
             _cancel_active_tasks=AsyncMock(return_value=0),
+            discard_session_file_state=MagicMock(),
             runtime_for_session=MagicMock(return_value=MagicMock()),
             schedule_background=lambda coro: asyncio.ensure_future(coro),
         )

tests/test_nanobot_facade.py

@@ -1500,10 +1500,15 @@ async def test_session_helpers_get_list_export_clear_delete_flush(tmp_path):
     exported.messages[0]["content"] = "mutated copy"
     assert bot.sessions.get("sdk:first").messages[0]["content"] == "hello"
 
+    state_before_clear = bot._loop._file_state_store.for_session("sdk:first")
     cleared = bot.sessions.clear("sdk:first")
     assert cleared.messages == []
+    state_after_clear = bot._loop._file_state_store.for_session("sdk:first")
+    assert state_after_clear is not state_before_clear
     assert bot.sessions.flush() >= 1
+    state_before_delete = state_after_clear
     assert bot.sessions.delete("sdk:first") is True
+    assert bot._loop._file_state_store.for_session("sdk:first") is not state_before_delete
     assert bot.sessions.get("sdk:first") is None
 
 

tests/tools/test_file_state_store.py

@@ -0,0 +1,29 @@
+import pytest
+
+from nanobot.agent.tools.file_state import FileStateStore
+
+
+def test_file_state_store_evicts_least_recently_used_session() -> None:
+    store = FileStateStore(max_sessions=2)
+    first = store.for_session("first")
+    second = store.for_session("second")
+
+    assert store.for_session("first") is first
+    store.for_session("third")
+
+    assert store.for_session("first") is first
+    assert store.for_session("second") is not second
+
+
+def test_file_state_store_discards_reset_session() -> None:
+    store = FileStateStore()
+    previous = store.for_session("websocket:chat")
+
+    store.discard("websocket:chat")
+
+    assert store.for_session("websocket:chat") is not previous
+
+
+def test_file_state_store_requires_positive_capacity() -> None:
+    with pytest.raises(ValueError, match="max_sessions must be positive"):
+        FileStateStore(max_sessions=0)